Transradial Access for Cardiovascular Catheterization and Intervention

introduction

Although both diagnostic coronary angiography and percutaneous coronary intervention (PCI) are still most commonly performed via transfemoral access in a large number of catheterization laboratories in the United States, the transradial access is now the default approach in Europe and Asia, accounting for more than 80% of PCI procedures. The development of highly potent antithrombotic regimens associated not only with a major reduction in thrombotic complications of PCI, but also with an increase in femoral access-site–related bleeding complications, has led to the development of the transradial approach (TRA) for PCI during the past two decades. While TRA adoption in the United States has been relatively slow, recent reports document a steady increase, now encompassing 30% to 40% of PCI. Similarly, primary PCI is more and more frequently performed with TRA, as shown in the international randomized Acute ST-elevation myocardial infarction (STEMI) Treated With Primary Angioplasty and Intravenous Enoxaparin or unfractionated heparin (UFH) to Lower Ischemic and Bleeding Events at Short- and Long-Term Follow-Up (ATOLL) study, in which 66% of procedures used the radial artery. The growing interest in TRA is also apparent in the medical literature, as more than 1500 publications concerning the subject have been reported within the past 5 years.

Rationale for Transradial Approach to Percutaneous Coronary Intervention

Feasibility and Security

Following the initial study in 1989, the feasibility and safety of TRA for coronary diagnostic or interventional procedures have been widely demonstrated by studies in the 1990s and early 2000s showing rates of successful PCI ranging from 90% to 100%.

As with any technique, TRA requires a learning curve, which has been ascribed to be less than 100 cases. Beyond that curve, experience leads to higher rates of procedural success and lower x-ray exposure. A recent meta-analysis demonstrated that, although they are associated with a statistically significantly higher operator x-ray exposure, the difference between transradial and transfemoral approaches becomes less significant with operators’ experience. The importance of the learning curve was also highlighted by the American National Cardiovascular Data Registry (NCDR), based on a study population of 54,561 patients. It showed that, on the one hand, as the operators’ transradial intervention volume increases, more high-risk patients are treated, whereas on the other hand, fluoroscopy time, contrast volume, and bleeding risk are reduced. The threshold to overcome the learning curve is still debated but is around 30 to 50 cases.

Both operator and patient x-ray exposures may be reduced by simple methods such as reducing the fluoroscopy rate from 15 to 7.5 frames per second, using leaded shields and patient support (e.g., starsystem), as well as maintaining the longest distance between x-ray source and operators. The recently developed robotic-assisted PCI solutions—Corindus, Robocath—may, in the future, dramatically reduce the operators’ x-ray exposure regardless of the vascular approach.

Overall the feasibility of a TRA for diagnostic or interventional coronary procedures is high (>90%), especially in experienced centers (>95%). In a series of 1119 consecutive South Korean patients, the mean radial artery diameter measured by ultrasound was 2.6 (±0.41) mm in men and 2.43 (±0.38) mm in women. In another series of 250 Japanese patients, the radial artery diameter was larger than 7- and 8-Fr catheters in 71.5% and 44.9% of male patients, respectively, and 40.3% and 24% of female patients, respectively. Although such data may not be totally generalized to all other populations, it underlies the fact that the TRA could potentially be used in a vast majority of patients with 5-, 6-, and even 7-Fr catheters. In some patients with sufficiently large artery diameter, 8-Fr catheters may also be used if needed. Yet it must be remembered that catheter–radial artery diameter mismatch is associated with a higher risk of radial artery occlusion.

TRA has been used for different types of procedures with various devices and methods such as intravascular ultrasound (IVUS)–guided stenting, coronary brachytherapy, distal protection, embolectomy, rotational atherectomy, bifurcated stents, and so on. However, this approach is still incompatible with the intraaortic balloon pump (IABP) and all other devices or procedures needing 8-Fr or greater access. It is interesting to note that TRA is now becoming more popular for peripheral interventions too.

The use of sheathless guiding catheters with smaller outer diameters—6.5- and 7.5-Fr catheters, equivalent to 5- and 6-Fr introducer diameters, respectively—has been reported to be feasible and safe. Although their use remains somewhat limited, such catheters may allow more complex procedures, such as simultaneous “kissing” stenting, in patients with small radial arteries.

More recently, the 5- to 7-Fr thin-walled slender sheaths with outer diameters smaller than standard sheaths have been developed. The 6-Fr slender was compared to a 5-Fr standard sheath in a multicenter study reporting no significant difference between the two groups in terms of radial artery occlusion rates. However, the noninferiority for the slender sheath was not demonstrated because of the very low event rates. If confirmed by further studies, such technology may allow the use of larger devices in small radial arteries.

TRA may be somewhat limited in patients who have previously undergone CABG. A recently published small ( n = 128) monocentric randomized study in this setting (58% diagnostic angiography alone) reported higher crossover rates, contrast volume, procedure time, and patient and operator exposure in the global group associated with a left transradial compared with a transfemoral approach. Nevertheless, as acknowledged by authors (most of them trained femoralists), with the first operator being always a trainee, the study may have been biased for the radiation exposure and contrast volume parameters. Furthermore, in the subgroup of patients who underwent PCI, procedural success was similar between the two groups. In patients with a left mammary graft, it is usually easier to cannulate the ostium selectively by using a left radial approach. However, selective catheterization of left or right internal thoracic bypasses is often possible via the contralateral approach, such as by using a Judkins left or other dedicated catheter. In patients with bilateral left internal thoracic bypasses, technical difficulties can be overcome easily by a bilateral radial access.

In a recent publication from a high radial volume center with a radial-first strategy, based on a consecutive series of more than 1600 patients, a transfemoral approach was directly used in 2.7% of patients, and in another 1.8%, it was used after a failed attempt at a TRA. Female sex, previous CABG, and cardiogenic shock were independent predictors of TRA failure.

Transradial Versus Transfemoral Approach for Percutaneous Coronary Intervention

The transfemoral approach represents an easily accessible superficial arterial access point, through which large catheters delivering all types of devices could be introduced. Compared with the transfemoral approach, TRA is associated with fewer vascular complications, more comfort for patients, and the possibility of rapid ambulation, lower procedure cost, and reduced hospital stay and cost. Several randomized trials comparing advantages and disadvantages of each method are summarized in Table 32.1 .

The first landmark international randomized trial comparing the transradial and transfemoral approaches was the Radial Versus Femoral Access for Coronary Intervention (RIVAL) trial, which included 7021 acute coronary syndrome (ACS) patients randomly assigned to each of the approaches for angiography and/or PCI. Indications for angiography were ST-elevation myocardial infarction (STEMI) in 27.2% and 28.5%, and non-STEMI (NSTEMI) in 28.5% and 25.8% in transradial and transfemoral groups, respectively. Angiography was performed in 99.8% and PCI was performed in approximately 66% of patients in both groups. PCI success rates were comparable between the two groups (95.4% vs. 95.2%), with higher access-site crossover rates in the transradial group (7.6% vs. 2%, P < .0001). The rates of the primary end point—the composite of death, myocardial infarction (MI), stroke, or non-CABG bleeding at 30 days—were comparable between the transradial and transfemoral groups (3.7% and 4%) as were each of the individual components. However, the secondary end point of major vascular complications occurred more often in the transfemoral group (1.4% vs. 3.7%, P < .0001). Moreover, all post hoc exploratory outcomes including major bleeding, the composite of death or MI or major bleeding and the composite of major non-CABG bleeding and vascular complications were met more often in the transfemoral group.

Although RIVAL failed to show a significant difference between the two groups regarding the primary end point used in the protocol, two major findings in the subgroup analysis should be underlined: first, in the STEMI subgroup of the study, the TRA was associated not only with a significant reduction of the primary end point, but also a reduction in mortality; second, the primary end point was also significantly reduced by the TRA in the centers with the highest radial PCI volume (hazard ratio [HR] 0.49; 95% confidence interval [CI] 0.28 to 0.87), which highlights the importance of the learning curve and operator experience for the TRA. The results of the RIVAL trial in the setting of ACS were more recently confirmed in the Minimizing Adverse Haemorrhagic Events by TRansradial Access Site and Systemic Implementation of angioX (MATRIX Access) trial, which randomly assigned 8404 ACS patients with or without ST-segment elevation, to radial or femoral access for angiography and PCI. The study showed a reduction of major adverse cardiovascular events, (relative risk [RR] 0.85; P = .03), net adverse clinical events (NACEs) (RR 0.83; P = .009), major bleeding unrelated to coronary artery bypass surgery (RR 0.67; P = .013) and all-cause mortality (RR 0.72; P = .045). The results were consistent among all patient subgroups, including the ACS presentation type, with the exception of a significant interaction, supporting the highest benefit in high radial volume centers. A meta-analysis of studies comparing transradial versus transfemoral approach in the setting of ACS incorporated in the latter publication confirmed the significant benefit of TRA in reducing rates of death, major cardiovascular events, and major non-CABG bleeding.

The overall advantages of TRA also have been underscored by three meta-analyses showing an initial higher procedural success rate for the transfemoral approach, but a clear trend toward equalization of procedural success rates between the two approaches through the years, and significant advantages of TRA in terms of bleeding complications, mainly through a dramatic reduction of entry-site complications as well as composite end points of cardiovascular events, including mortality.

Such advantages make the TRA the access of choice for same-day PCI, which has been reported to be highly feasible, safe, and cost effective in such indication. Several centers in Europe and the United States are now introducing the concept of “radial lounges” to accommodate patients before and after catheterization in an environment similar to an “airport lounge.”

The TRA is also of particular interest in patients at high risk for bleeding (older adults, women, patients with renal failure, the obese, or patients on multiple antithrombotic agents, especially glycoprotein [GP] IIb/IIIa inhibitors). The TRA has been reported to be associated with fewer vascular complications in obese patients (multivariate odds ratio [OR] 0.12; 95% CI 0.02 to 0.94; P = .043) in a retrospective series of 5234 diagnostic or interventional (56.6%) procedures, as well as in older adults (1.6% vs. 6.5%, P = .03). Other patients with obvious advantages for a radial, rather than a femoral, approach are patients with severe and/or proximal peripheral artery disease (PAD), patients with bilateral aortofemoral bypass grafts, those with aortic aneurysms, and patients with a prior history of femoral complication after catheterization. Unfortunately, data from NCDR registry illustrated the so-called “radial paradox” in which higher bleeding-risk patients are, in fact, less likely to undergo TRA in U.S. centers.

TRA has been associated with reduced risks of acute kidney injury compared to the transfemoral approach concordantly demonstrated in different patient cohorts. Such findings may be related to the reduced atheroembolic potential of the transradial access. Yet, further data from randomized comparison are required to better establish the mechanism of TRA impact and the magnitude of benefit for TRA compared to standard femoral access.

Finally, when considering all-comer PCI registries such as the RIVIERA registry, which prospectively included 7962 unselected patients or the Canadian MORTAL registry of 38,872 procedures, the TRA appears to be independently associated to reduced rates of bleeding, death, or MI, at 30-day and 1-year mortality.

The 2007–12 report of the NCDR ( n = 2,820,874 procedures) comparing transradial and transfemoral approaches confirmed the prior findings with overall higher success rates (94.7% vs. 93.8%, adjusted OR 1.13, P < .001) and fewer vascular (0.16% vs. 0.45%, adjusted OR 0.51, P < .001) and bleeding complications (2.67% vs. 6.08%, adjusted OR 0.39, P < .001) with the TRA.

Transradial Approach in St-Elevation Myocardial Infarction

TRA is of particular interest in the setting of primary PCI for STEMI ( Tables 32.1 and 32.2 ) performed by experienced operators in patients treated by aggressive antithrombotic regimens, in which life-threatening access-site bleeding complications and the subsequent major cardiovascular events may be avoided by such an approach. In this setting, growing evidence suggests that TRA is associated with overall similar door-to-balloon times, lower rates of vascular complication and bleeding in the presence of triple antithrombotic therapy, and even reduced 30-day mortality compared with a femoral approach. As mentioned above, in the STEMI subgroup of the RIVAL trial, TRA was associated not only with a significant reduction of the primary end point (HR 0.6; 95% CI 0.38 to 0.94), but also with mortality (HR 0.39; 95% CI 0.20 to 0.76).

Two studies in the specific setting of PCI for STEMI confirmed overall the superiority of the transradial versus the transfemoral approach in terms of NACEs, combining bleeding, and thrombotic events. Moreover, the Radial Versus Femoral Randomized Investigation in ST-Elevation Acute Coronary Syndrome (RIFLE-STEACS) trial reported a highly significant reduction of 30-day mortality and bleeding associated with a TRA (5.2% vs. 9.2%, P = .02, and 7.8% vs. 12.2%, P = .03). Although the benefit of the TRA in terms of mortality were not specifically demonstrated in the MATRIX trial, the recently published comparison of STEMI versus non-ST ACS patients included in the trial showed that the results were consistent between groups of ACS patients based on the type of presentation. Table 32.2 summarizes the results of the TRA versus transfemoral studies in the setting of STEMI.

A recent meta-analysis of 16 randomized trials, confirmed the latter data showing significant and consistent reductions in all-cause mortality (RR 0.68; 95% CI 0.54 to 0.85), major adverse cardiac events (RR, 0.80; 95% CI 0.68 to 0.94), and major bleeding (RR 0.56; 95% CI 0.42 to 0.74) by the transradial compared with the transfemoral approach. It should be remembered that the exact mechanisms on how TRA might directly impact on survival benefit in primary PCI compared to femoral approach remains largely unknown and are likely multifactorial.

Finally, although based on observational studies, the feasibility and the benefit of the TRA seem to be preserved even in the setting of cardiogenic shock complicating STEMI.

Considering such compelling data, the latest European Society of Cardiology (ESC) guidelines for the management of STEMI recommended a transradial over a transfemoral approach in the setting of primary PCI (level of recommendation Ia). Upcoming statements from U.S. scientific societies will also recommend higher use of TRA in catheterization laboratories.

Transradial Versus Transbrachial Approaches

Two of the previous randomized trials also had a transbrachial approach subgroup of patients. The Radial Versus Femoral Access for Coronary Angiography of Intervention and the Impact on Major Bleeding and Ischemic Events (ACCESS) study reported comparable procedural success rates, equipment consumption, and procedural and fluoroscopy time among the three approaches for PCI. Nevertheless, the transbrachial approach was associated with higher rates of vascular complications compared with the TRA (2% vs. 0%, P = .035). The Brachial, Radial, or Femoral Approach for Elective Palmaz-Schatz Stent Implantation (BRAFE) stent study compared transradial and transfemoral approaches with a transbrachial cutdown approach, reporting no local vascular complication with the latter. Such a brachial approach is not commonly used anymore (outside Japan) and still bears a higher risk of vascular complications. The brachial access does not need a cutdown and can be done with a classic percutaneous approach, but it is usually preferred when neither femoral nor radial approaches are possible.